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libutil: add example for util_lockfile
Adds util_lockfile_example.c, which can be used to sample util_lockfile support. To acquire a lock using a parent PID (e.g. your shell instance): util_lockfile_exmample -f <path> -l <retries> To release the lock using the parent PID: util_lockfile_example -f <path> -r To acquire the lock, sleep briefly, and then release the lock using the PID of the util_lockfile_example process: util_lockfile_example -f <path> -L <retries> In each example, the <path> is the location of the desired lockfile and <retries> is the number of times to retry acquiring the lock if it fails. GitHub-ID: https://github.com/ibm-s390-linux/s390-tools/issues/142 Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com> Reviewed-by: Steffen Eiden <seiden@linux.ibm.com> Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>
This commit is contained in:
Matthew Rosato
committed by
Jan Höppner
Jan Höppner
parent
e1aec24e84
commit
6235a51d7c
232
libutil/util_lockfile_example.c
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232
libutil/util_lockfile_example.c
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/**
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* util_lockfile_example - Example program for util_lockfile
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*
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* Copyright IBM Corp. 2022
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*
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* s390-tools is free software; you can redistribute it and/or modify
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* it under the terms of the MIT license. See LICENSE for details.
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*/
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//! [code]
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#include <stdio.h>
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#include <stdlib.h>
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#include "lib/util_opt.h"
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#include "lib/util_prg.h"
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#include "lib/util_lockfile.h"
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static const struct util_prg prg = {
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.desc = "Example for util_lockfile.",
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.copyright_vec = { {
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.owner = "IBM Corp.",
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.pub_first = 2022,
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.pub_last = 2022,
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},
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UTIL_PRG_COPYRIGHT_END }
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};
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static struct util_opt opt_vec[] = {
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UTIL_OPT_SECTION("OPTIONS"),
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{
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.option = { "file", required_argument, NULL, 'f' },
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.argument = "PATH",
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.desc = "Use the specified path for a lockfile.",
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},
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{
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.option = { "lock", required_argument, NULL, 'l' },
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.argument = "RETRIES",
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.desc = "Acquire the specified file lock using the parent "
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"process id of this process. If not immediately "
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"successful, retry for the specified number of times",
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},
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{
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.option = { "release", 0, NULL, 'r' },
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.desc = "Release the specified lock file using the parent "
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"process id",
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},
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{
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.option = { "lock-and-release", required_argument, NULL, 'L' },
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.argument = "RETRIES",
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.desc = "Acquire the specified file lock using this process "
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"id, then release it. If not immediately successful, "
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"retry for the specified number of times.",
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},
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UTIL_OPT_HELP,
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UTIL_OPT_VERSION,
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UTIL_OPT_END
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};
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enum prg_action {
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ACTION_NONE = 0,
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ACTION_LOCK,
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ACTION_RELEASE,
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ACTION_LOCK_AND_RELEASE,
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};
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static void print_single_action_error(void)
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{
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warnx("Only a single action (--lock, --lock-parent, --release, "
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"--release-parent) is allowed");
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}
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int main(int argc, char *argv[])
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{
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enum prg_action action_id = ACTION_NONE;
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int opt, rc, retries = 0;
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char *endp, *path = NULL;
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util_prg_init(&prg);
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util_opt_init(opt_vec, NULL);
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while (1) {
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opt = util_opt_getopt_long(argc, argv);
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if (opt == -1)
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break;
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switch (opt) {
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case 'f':
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path = optarg;
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break;
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case 'L':
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if (action_id != ACTION_NONE) {
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print_single_action_error();
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return EXIT_FAILURE;
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}
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retries = strtol(optarg, &endp, 0);
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if (*optarg == '\0' || *endp != '\0' || retries < 0) {
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warnx("Invalid retry value for "
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"--lock-and-release: '%s'",
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optarg);
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util_prg_print_parse_error();
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return EXIT_FAILURE;
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}
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action_id = ACTION_LOCK_AND_RELEASE;
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break;
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case 'l':
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if (action_id != ACTION_NONE) {
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print_single_action_error();
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return EXIT_FAILURE;
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}
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retries = strtol(optarg, &endp, 0);
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if (*optarg == '\0' || *endp != '\0' || retries < 0) {
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warnx("Invalid retry value for "
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"--parent-lock: '%s'",
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optarg);
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util_prg_print_parse_error();
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return EXIT_FAILURE;
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}
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action_id = ACTION_LOCK;
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break;
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case 'r':
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if (action_id != ACTION_NONE) {
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print_single_action_error();
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return EXIT_FAILURE;
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}
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action_id = ACTION_RELEASE;
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break;
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case 'h':
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util_prg_print_help();
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util_opt_print_help();
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exit(EXIT_SUCCESS);
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case 'v':
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util_prg_print_version();
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exit(EXIT_SUCCESS);
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default:
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util_opt_print_parse_error(opt, argv);
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return EXIT_FAILURE;
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}
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}
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if (!path) {
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warnx("--file is required, see --help for more information");
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return EXIT_FAILURE;
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}
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if (action_id == ACTION_NONE) {
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warnx("One of the following actions must be specified: "
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"--lock, --release, --lock-and-release");
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return EXIT_FAILURE;
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}
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/* Determine which util_lockfile function to call */
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switch (action_id) {
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case ACTION_LOCK:
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rc = util_lockfile_parent_lock(path, retries);
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switch (rc) {
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case UTIL_LOCKFILE_OK:
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printf("lock acquired successfully\n");
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break;
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case UTIL_LOCKFILE_LOCK_FAIL:
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warnx("lock was not acquired; already held");
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return EXIT_FAILURE;
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case UTIL_LOCKFILE_ERR:
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warnx("lock was not acquired; file error");
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return EXIT_FAILURE;
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default:
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warnx("Unknown util_lockfile rc %d", rc);
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return EXIT_FAILURE;
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}
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break;
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case ACTION_RELEASE:
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rc = util_lockfile_parent_release(path);
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switch (rc) {
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case UTIL_LOCKFILE_OK:
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printf("lock released successfully\n");
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break;
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case UTIL_LOCKFILE_RELEASE_NONE:
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warnx("lock file did not exist");
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return EXIT_FAILURE;
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case UTIL_LOCKFILE_RELEASE_FAIL:
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warnx("lock was not held by the specified pid");
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return EXIT_FAILURE;
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case UTIL_LOCKFILE_ERR:
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warnx("lock was not released; file error");
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return EXIT_FAILURE;
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default:
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warnx("Unknown util_lockfile rc %d", rc);
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return EXIT_FAILURE;
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}
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break;
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case ACTION_LOCK_AND_RELEASE:
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rc = util_lockfile_lock(path, retries);
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switch (rc) {
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case UTIL_LOCKFILE_OK:
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printf("lock acquired successfully, holding for 2 seconds\n");
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break;
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case UTIL_LOCKFILE_LOCK_FAIL:
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warnx("lock was not acquired; already held");
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return EXIT_FAILURE;
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case UTIL_LOCKFILE_ERR:
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warnx("lock was not acquired; file error");
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return EXIT_FAILURE;
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default:
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warnx("Unknown util_lockfile rc %d", rc);
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return EXIT_FAILURE;
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}
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/* Briefly sleep while holding the lock */
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sleep(2);
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rc = util_lockfile_release(path);
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switch (rc) {
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case UTIL_LOCKFILE_OK:
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printf("lock released successfully\n");
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break;
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case UTIL_LOCKFILE_RELEASE_NONE:
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warnx("lock file did not exist");
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return EXIT_FAILURE;
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case UTIL_LOCKFILE_RELEASE_FAIL:
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warnx("lock was not held by the specified pid");
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return EXIT_FAILURE;
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case UTIL_LOCKFILE_ERR:
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warnx("lock was not released; file error");
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return EXIT_FAILURE;
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default:
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warnx("Unknown util_lockfile rc %d", rc);
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return EXIT_FAILURE;
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}
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break;
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default:
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warnx("Unknown util_lockfile action");
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return EXIT_FAILURE;
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}
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return EXIT_SUCCESS;
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}
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//! [code]
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